Embodiments of the present disclosure relate generally to a thermal spray gun. Specifically, the subject matter disclosed herein relates to a nozzle insert which may be used with a thermal spray gun apparatus.
Thermal spraying is a coating method wherein powder or other feedstock material is fed into a stream of heated gas produced by a plasmatron or by the combustion of fuel gasses. The hot gas stream entrains the feedstock, transferring heat and momentum thereto. The heated feedstock becomes a discharge that is further impacted onto a surface, where it adheres and solidifies, forming a thermally sprayed coating composed of thin layers or lamellae.
One common method of thermal spraying is plasma spraying. Plasma spraying is typically performed by a plasma torch or “spray gun,” which uses a plasma jet to heat or melt the feedstock before propelling it toward a desired surface. Current thermal spray guns operate efficiently (e.g., over 60% efficiency) at one power mode (e.g., 75 kW) and deliver one coat in one position with respect to a specimen. When spraying different coats and/or different specimens, extensive modifications to the spray gun may be necessary to adjust the discharge.
Spraying different specimens, or different portions of the same specimen, may require using different thermal spray guns with different power levels to generate varying plasma plumes and coatings. In order to spray a different type of coating, the thermal spray gun may be removed from the robotic arm and disassembled to install a replacement nozzle, after which the thermal spray gun can be reassembled. The assembly and reassembly process typically require a reservoir of cooling water to be opened, drained, and then refilled. Each thermal spray gun nozzle may be configured to emit a different plasma discharge. Physical properties of a plasma spray gun system, such as standoff distance, may change in response to the modified gun being mounted to a robotic arm configured for use with a different thermal spray gun. In this case, the robotic arm may require adjusting (e.g., via reprogramming). This reprogramming step may be inconvenient to the operator and cause delays in the spraying process.